Packaged semiconductor devices are utilized in cellular phones, pagers, personal digital assistants, computers and many other types of consumer or industrial electronic products. Microelectronics manufacturers are developing more sophisticated devices in smaller sizes. To meet current design criteria, semiconductor components have increasingly dense arrays of input/output terminals within decreasing “footprints” on printed circuit boards (i.e. the height and surface area the device occupies on a printed circuit board).
Semiconductor devices are typically fabricated on semiconductor wafers or other types of workpieces using methods that simultaneously process a large number of dies (i.e., chips). Microelectronic devices generally have a die that includes an integrated circuit having a high density of very small components. The dies typically include an array of bond-pads or other external electrical terminals for transmitting supply voltage, signals, etc. to and from the integrated circuitry. The bond-pads are usually very small and are assembled in dense arrays having fine pitches between bond-pads.
One technique to increase the density of microelectronic devices within a given footprint is stacking one microelectronic die on top of another. Through-substrate interconnects, for example, can electrically connect bond pads at a front side of a lower die with contacts at a back side of the lower die such that bond pads of a top die can be electrically coupled to the back side contacts of the lower die. An existing process for stacking such dies includes thinning first and second wafers by removing material from the back side of the wafers to (1) expose interconnect contact points on the back side of the dies, and (2) reduce the thickness of the dies. The second wafer is generally thinned to not less than 300 microns. After thinning, the second wafer is singulated (i.e., cut) and separate dies from the second wafer are stacked onto dies on the first wafer. An encapsulant is subsequently disposed between individual second dies, and the first wafer and encapsulant are cut to separate stacked devices.